Rihanna posted the message just as Aguilera’s talent competition show “The X Factor” wrapped its second season premiere. Furthermore, “#DIRRRTY” seemed a likely reference to Aguilera’s song “Dirrty” off the album “Stripped” in 2002.

Rihanna and Aguilera have teamed up in the past. Both pop stars performed on the British version of “The X Factor” in 2010, eliciting complaints for their skimpy costumes and suggestive dance moves.

Rihanna is known for her collaborations with other stars. She has worked with Jay-Z, Britney Spears, Drake, Nicki Minaj, Eminem and Justin Timberlake in the past.